Electrical contractors use crimpable connectors to form terminations on various copper and aluminum wires. Examples of such connectors are described in UL Standard 486 provided by Underwriters Laboratories, Inc. A variety of crimping tools and crimp profile die geometries are used. Although many different types of dies are used in the field, all dies require a linear application of force to plastically form the connector and wire to the internal geometry of the die. A wide variety of such tools are commercially available from suppliers such as Burndy, Greenlee, and Klauke.
Crimp tools typically require about 53 to 130 kN of linear force and 18 to 32 mm of travel in order to perform a crimping operation. Because of the high amount of work capacity involved, the tools are typically large and heavy. For example, a 130 kN tool may weigh as much as 15 pounds. Electrical contractors use the tools in a variety of applications which require that they hold the tool in one hand. Because of this, weight is a primary concern of users. Thus, it is highly desirable to design a tool which is optimized for weight in order to increase ease of use of the tool.
Generally, these crimp tools utilize a C-frame crimping head. The C-frame crimping heads are subjected to high stresses during a crimping operation and thus are typically formed from a high tensile strength material, for example hardened alloy steel, and require a large cross section. The weight of a C-frame crimping head is relatively heavy and optimization efforts are focused on this component.
As crimping tools are presently configured, optimization of the C-frame head is limited by two constraints. One constraint is that the C-frame head must not be allowed to deflect at the open end. Such deflection results in displacement of the dies in a nonlinear or substantially nonlinear manner. In many instances, the dies are displaced away from a generally linear travel path during a crimping operation. In such an event, the dies may become misaligned and the crimp profile may be distorted. In the industry, a crimp is generally considered complete when both ends of the crimp inserts or dies are in contact with each other. The noted problems with deflection can prevent this from occurring, particularly with large connectors. Additionally, the stresses on mating parts are increased and mechanical failures may result. Another constraint is that the maximum stress in the C-frame head must be limited and controlled so as to prevent premature failure and ensure an appropriate failure mode.
Due to the geometry of the components and applications of the loads, the deflection constraint is more restrictive. For example, a C-frame head optimized only for stress has been shown to be lighter. However, a lighter and more flexible C-frame head has also been shown to cause damage to mating parts as a result of the deflection.
Accordingly, a need exists for a C-frame head, such as used in a pressing tool or crimping tool, which avoids these problems, and particularly for such a tool which exhibits a lightweight design, yet which avoids or at least reduces the potential of damage resulting from deflection.